Collections - The Java Programming Language - page 909

of the ArrayBunchList will go through set , which modifies the appropriate
underlying array.
AbstractList provides Iterator and ListIterator implementations on top
of the other methods of the class. Because the iteration implementations
use the methods of your underlying subclass of AbstractList , the modi-
fying methods of the iteration will properly reflect the modifiability of
your class.
The Iterator implementations of AbstractList use get to read values. As
you will note, ArrayBunchList has a get that can do some significant work
if the value is stored in one of the later arrays. We can make get smarter
than shown here to help with this work, but we can be even more effi-
cient for iteration because it accesses the data sequentially. Here is an
optimized Iterator :
private class ABLIterator implements Iterator<E> {
private int off; // offset from start of list
private int array; // array we are currently in
private int pos; // position in current array
ABLIterator() {
off = 0;
array = 0;
pos = 0;
// skip any initial empty arrays (or to end)
for (array = 0; array < arrays.length; array++)
if (arrays[array].length > 0)
break;
}
public boolean hasNext() {
return off + pos < size();
}
public E next() {
if (!hasNext())
throw new NoSuchElementException();
E ret = arrays[array][pos++];